The IMOD software package provides tools for generating, viewing, and analyzing 3-dimensional (3-D) image data, with a focus on tools for tomography, which involves the reconstruction of the interior of a specimen from a series of tilted views obtained with an electron microscope. The use of tomography has been growing rapidly in cell and structural biology research and there is potential for wider use in other areas of biomedical research. The long-term goals of this project are to develop the software further so that it continues to offers a powerful and attractive package for tomographic reconstruction as methods evolve, and to provide a resource that can be both used and built upon by others in the microscopy community. The first aim is to maintain and optimize the function of the software in various ways on multiple platforms (Linux, Microsoft Windows, Macintosh OS X), adapting to and taking advantage of continual improvements in hardware and system software. A second aim is to add new features in response to users' needs. This work includes enhancing the graphical modeling program in IMOD for better analysis and visualization of 3-D data, and continually modifying the user interface for tomographic reconstruction to provide access to improved algorithms as they are developed. User interfaces and documentation will also be upgraded to make the software easier to use. A third aim is continue improving the management and documentation of the software, with an emphasis on expanding automated testing. These improvements will enhance the software's reliability and make it more easily extensible both by us and by others who wish to build on IMOD's capabilities.